The structure of an aircraft, as we know, comprises a plurality of spaced out transverse frames locked together with longerons, said structure being covered with the shell of the aircraft. Also, in certain cases, in particular in the case of transport aircrafts, some at least of the structural frames, which are required to have high mechanical strength, are constituted of an annular underframe generally formed by a curvilinear section and reinforced in parts by girders sub-tending parts of said underframe. While such girders confer to the corresponding frames is required mechanical strength properties, in order to enable the aircraft to withstand the most severe operating conditions, they also restrict the size of the central opening defined by said frames, hence the maximum dimensions of the cargo which can be loaded into the aircraft.
It often happens that certain cargoes cannot be loaded into a cargo plane because their overall size exceeds by a few centimeters the corresponding size of the hatch area. It may also happen, in the case of a transport aircraft with a rear door designed to serve as an inclined ramp for loading the cargo, that said cargo cannot go through the opening or hatch area of the structural frame situated vertically to the upper part of the ramp, just because of the inclination of said ramp, whereas the dimensions of the load would enable it to be loaded through said frame if the direction of introduction were horizontal instead of being upwardly inclined. In this case, the only thing would be to raise the nose of the transport aircraft so as to bring the ramp and the floor of the aircraft into alignment. This measure, besides being complicated and delicate, may even prove insufficient.
One solution to try and solve this problem, could be to permanently modify the girder or girders preventing the loading of the cargo; but this solution could only be applied with the consent of the constructor of the aircraft and would involve a revision of the aircraft certificate of airworthiness. Another solution could be to temporarily remove those frame girders in the way for loading or unloading a cargo; but then, as the aircraft structure is subjected to very high stresses on the ground, there could be a risk of unacceptable deformations and reductions of mechanical strength.